Tegretol prolonged release (carbamazepine)

Tegretol prolonged release tablets contain the active ingredient carbamazepine, which is a medicine that is mainly used to treat epilepsy. It works by stabilising electrical activity in the brain. Carbamazepine is also available without a brand name, ie as the generic medicine.

What is Tegretol used for?

As a mood stabiliser in bipolar affective disorder to help prevent episodes of mania or depression, when lithium has not been effective.

Severe pain in the lips, gums, cheek, chin or eye caused by a disorder of the nerves in the face (trigeminal neuralgia).

Pain due to nerve damage in people with diabetes (diabetic neuropathy). This is an unlicensed use of carbamazepine.

How does Tegretol work?

Tegretol prolonged release tablets (previously called Tegretol Retard tablets) contain the active ingredient carbamazepine, which is a medicine that is mainly used to treat epilepsy. It works by stabilising electrical activity in the brain.

The brain and nerves are made up of many nerve cells that communicate with each other through electrical signals. These signals must be carefully regulated for the brain and nerves to function properly. When abnormally rapid and repetitive electrical signals are released in the brain, the brain becomes over-stimulated and normal function is disturbed. This results in fits or seizures.

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Carbamazepine prevents epileptic fits by preventing the excessive electrical activity in the brain. It is thought to achieve this by preventing sodium from entering nerve cells when they begin to fire rapid and repetitive electrical signals. A build up of sodium in the nerve cells is necessary for the electrical signal to build up and be passed on to other nerve cells. As carbamazepine prevents this, it helps stabilise the electrical activity in the brain.

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Preventing the build-up of the electrical signal also prevents the release of a neurotransmitter called glutamate from the nerve cells in the brain. Neurotransmitters are chemicals that are stored in nerve cells and are involved in transmitting messages between the nerve cells. Glutamate is a neurotransmitter that acts as a natural 'nerve-exciting' agent. It is released when electrical signals build up in nerve cells and subsequently excites more nerve cells. It is thought to play a key role in causing epileptic seizures. Reducing the release of glutamate from the nerve cells in the brain is another way in which carbamazepine is thought to help stabilise the electrical activity in the brain and prevent epileptic fits.

As carbamazepine stabilises electrical nerve activity, it is also used to treat a condition called trigeminal neuralgia, in which the facial nerves spontaneously send messages of pain to the brain. Carbamazepine prevents the nerve signals being sent inappropriately and relieves the pain of this condition.

Carbamazepine is also used as a mood stabiliser for treating people with the psychiatric illness, bipolar affective disorder. It is licensed for preventing episodes of ill health (abnormally high and low mood) in people with bipolar disorder who have not responded to the older mood stabiliser, lithium. It is particularly useful for people who experience multiple mood swings (rapid cycling). Carbamazepine is also used off-licence by specialists to control episodes of mania in this illness. It is not fully understood how carbamazepine works as a mood stabiliser, but is thought to be to do with the reduction of glutamate activity in the brain.

Tegretol prolonged release tablets are designed to release the carbamazepine slowly and continuously over a few hours to help provide steady blood levels of the medicine throughout the day. These tablets must not be crushed or chewed as this would damage the prolonged release action.

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How do I take Tegretol prolonged release tablets?

Tegretol prolonged release tablets can be taken either with or without food.

The tablets are scored and can be broken in half, however they must not be crushed or chewed.

The dose of this medicine that is prescribed and how often the medicine needs to be taken will vary from person to person depending on the condition being treated and how well it is controlled. The dose will be increased gradually to start with. It is important to follow the instructions given by your doctor. These will also be printed on the dispensing label that your pharmacist has put on the packet of medicine. If you are unsure about anything ask your doctor or pharmacist for advice.

If you forget to take a dose, take it as soon as you remember. However, if it is nearly time for your next dose, leave out the missed dose and take your next dose as usual when it is due. Do not take a double dose to make up for a forgotten dose.

If you have epilepsy it is important to take your medication regularly, as directed by your doctor, because missing doses can trigger seizures in some people. If you have trouble remembering to take your medicine you should ask your pharmacist for advice. You may find a pill reminder box helpful.

You should not suddenly stop taking this medicine unless your doctor tells you otherwise, as suddenly stopping treatment is likely to make your condition come back or get worse. If this medicine is stopped, it should normally be done gradually, under the supervision of your specialist.

Important information about Tegretol

This medicine may cause dizziness, drowsiness and disturbances in vision such as blurred or double vision. You should take care when performing potentially hazardous activites, such as driving or operating machinery, until you know how this medicine affects you and are sure you can perform such activities safely.

It is recommended that you avoid drinking grapefruit juice while taking this medicine. This is because grapefruit juice can affect the metabolism of carbamazepine and could increase the amount of the medicine in your blood, thus increasing the risk of side effects.

This medicine can sometimes cause a decrease in the normal amounts of blood cells in the blood. For this reason you should consult your doctor immediately if you experience any of the following symptoms, as they may indicate a problem with your blood cells: unexplained bruising or bleeding, purple spots, sore throat, mouth ulcers, high temperature (fever), feeling tired or general illness. Your doctor may want to take a blood test to check your blood cells.

This medicine may rarely cause liver problems. For this reason you should consult your doctor promptly if you develop any of the following symptoms while taking this medicine, as they may indicate a problem with your liver: unexplained itching, yellowing of the skin or eyes, unusually dark urine or pale stools, nausea and vomiting, abdominal pains, loss of appetite or flu-like symptoms.

While taking this medicine your doctor will want you to have regular blood tests to monitor your liver function and the number of blood cells in your blood.

This medicine may very rarely cause serious allergic reactions, including potentially life-threatening skin reactions (Stevens Johnson syndrome and toxic epidermal necrolysis). If you get a skin rash, blistering or peeling of the skin, ulcers in the mouth, throat, nose, or genitals, red and sore eyes, a fever or swollen glands while taking this medicine, you should consult your doctor urgently.

There may be a small increased risk of suicidal thoughts and behaviour in people taking antiepileptic medicines such as carbamazepine for any condition. For this reason, it is very important to seek medical advice if you, or someone else taking this medicine, experience any changes in mood, distressing thoughts, or feelings about suicide or self-harm at any point while taking this medicine. For more information speak to your doctor or pharmacist.

Carbamazepine makes hormonal contraceptives that contain oestrogen and/or progesterone (such as the pill or patch) ineffective at preventing pregnancy. It is important for women who could get pregnant to discuss pregnancy and methods of contraception with their doctor before starting treatment with this medicine.

Tegretol should not be used in

People who have a problem with the electrical message pathways in the heart called atrioventricular (AV) block.

People with a history of decreased blood cell production by the bone marrow (bone marrow depression).

Hereditary blood disorders called porphyrias.

People who are allergic to tricyclic antidepressants, eg amitriptyline.

People with a history of psychotic illness (involving delusions, paranoia or hallucinations).

People with raised pressure in the eye (intraocular pressure), eg glaucoma.

People with an underactive thyroid gland (hypothyroidism). Your thyroid hormones should be monitored as this medicine may cause you to need an increase in your dose of thyroxine.

People who have previously experienced problems with their blood cells as a result of taking any other medication.

People who have previously had to interrupt treatment with carbamazepine due to side effects or allergy.

People of Thai or Han Chinese ethnic origin (some people may have a genetic variant that increases the risk of getting a serious skin reaction - see above).

People who don't consume much calcium in their diet, don't get enough vitamin D from exposure to sunlight or are immobilised for long periods of time, for example due to being confined to bed or having a leg in a plaster cast. If you fall into any of these groups your doctor may want you to take a vitamin D supplement if you are taking carbamazepine for a long time. This is because carbamazepine can interfere with the way the body metabolises vitamin D and calcium, which can cause bone thining and weakening, osteomalacia, osteoporosis and an increased risk of fractures. Ask your doctor or pharmacist for more information. If you have a history of osteoporosis or are also taking long-term corticosteroids these are further risk factors for osteoporosis and you should discuss this with your doctor.

Pregnancy and breastfeeding

Certain medicines should not be used during pregnancy or breastfeeding. However, other medicines may be safely used in pregnancy or breastfeeding providing the benefits to the mother outweigh the risks to the unborn baby. Always inform your doctor if you are pregnant or planning a pregnancy, before using any medicine.

It is vital that women with epilepsy receive specialist advice regarding contraception, pregnancy and planning a family before they start treatment for their condition and before they get pregnant. Pregnant women taking antiepileptic medicine have a higher risk of carrying a baby with developmental problems and malformations than other women. This risk increases if more than one antiepileptic is being taken to control seizures. However, if a woman with epilepsy stops treatment because she gets pregnant, this is likely to cause seizures that can potentially be more harmful to both mother and baby than continuing treatment.

Clearly it is important to avoid an unplanned pregnancy while taking an antiepileptic medicine by using an effective method of contraception. You will need to discuss this with your doctor, because carbamazepine makes the pill, mini-pill, patch and vaginal ring ineffective at preventing pregnancy. There are various methods that are not affected by carbamazepine; these include the IUD (eg Mirena), contraceptive injection and barrier contraceptives such as condoms. Another option is to take take two pills together to get a higher dose of hormones, however this is not suitable for all women and is also unlicensed. It is important to get advice from your doctor.

If you think you could be pregnant while taking this medicine it is vital that you consult your doctor straight away for advice. Don't stop taking this medicine unless your doctor tells you to.

Women who decide to try for a baby while taking carbamazepine should start taking folic acid daily as soon as contraception is stopped, as this may reduce the risk of neural tube defects such as spina bifida in the baby. Ask your doctor for advice on the dose to take - it may be recommended that you take 5mg daily.

This medicine passes into breast milk. The benefits of breastfeeding should be weighed against any possible risks to the infant. However, it is usually possible to breastfeed your baby if you are taking carbamazepine on its own and your baby was not born prematurely and has no other health issues. It is important to get medical advice from your doctor. Breast-fed infants should be observed for possible adverse reactions of the medicine, such as excessive drowsiness, skin rashes or liver problems. Discuss this with your doctor.

Possible side effects of Tegretol

Medicines and their possible side effects can affect individual people in different ways. The following are some of the side effects that are known to be associated with this medicine. Just because a side effect is stated here does not mean that all people using this medicine will experience that or any side effect.

Very rare (affect fewer than 1 in 10,000 people)

Other skin reactions such as change in hair growth, increased sweating or increased sensitivity to sunlight.

Weakening of the bones. See the cautions above.

Pain in the muscles or bones.

Kidney problems.

Sexual problems, such as erectile dysfunction or reduced sperm count or motility.

Serious disturbances in the normal numbers of blood cells in the blood. See the warning section above.

Hearing problems.

Problems with the heart, such as an irregular or slow heart beat or heart failure.

The side effects listed above may not include all of the side effects reported by the medicine's manufacturer. For more information about any other possible risks associated with this medicine, please read the information provided with the medicine or consult your doctor or pharmacist.

If you think you have experienced a side effect from a medicine or vaccine you should check the patient information leaflet. This lists the known side effects and what to do if you get them. You can also get advice from your doctor, nurse or pharmacist. If they think it's necessary they'll report it for you.

How can Tegretol affect other medicines?

Carbamazepine can interact with many medicines and the dose of carbamazepine or the interacting medicine may need to be altered as a result. It is important to tell your doctor what medicines you are taking, including herbal medicines and non-prescription medicines, before you start carbamazepine. Likewise, once you are taking carbamazepine it is important to check with your doctor or pharmacist before you stop taking any existing medicines, or start taking any new medicines, including herbal medicines and those bought without a prescription.

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The manufacturer states that carbamazepine should not be taken in combination with monoamine oxidase inhibitor antidepressants (MAOIs, eg phenelzine, tranylcypromine, isocarboxazid). At least two weeks should pass after stopping an MAOI before starting carbamazepine.

The effects of carbamazepine on other anticonvulsant medicines and of other anticonvulsants on carbamazepine, are fairly unpredictable. If more than one anticonvulsant is being used at the same time, the blood levels of the medicines, their effect on seizures, and the emergence of side effects should be well monitored.

The following medicines may reduce the breakdown of carbamazepine in the body. As this could increase the level of carbamazepine in your blood and may increase the risk of side effects, your doctor may need to decrease your carbamazepine dose if you are prescribed any of these:

The following medicines may increase the breakdown of carbamazepine in the body. As this could decrease the level of carbamazepine in your blood and may make it less effective, your doctor may need to increase your carbamazepine dose if you are prescribed any of these:

isotretinoin

theophylline

rifabutin

rifampicin

the herbal remedy St John's wort (Hypericum perforatum). This should not be taken by people who are taking carbamazepine.

Carbamazepine may increase the breakdown of the following medicines in the body. As this could decrease the level of these medicines in the blood and may make them less effective, your doctor may need to prescribe a larger than normal dose of these:

oestrogens and progestogens such as those in the contraceptive pill, patch or vaginal ring. (Carbamazepine can make these types of contraceptive ineffective, or cause breakthrough bleeding. Women taking carbamazepine who need a contraceptive should preferably be prescribed contraceptives that are not affected by carbamazepine, such as the contraceptive IUD or injection. Alternatively, two combined pills containing a total of at least 50 micrograms of ethinylestradiol can be used and these must also be taken in three-monthly cycles. This means having a weeks break from pill taking every three months instead of every month. This is unlicensed and it is important to discuss your contraceptive options with your doctor.)

ulipristal (the morning-after pill containing ulipristal (EllaOne) should not be used for emergency contraception in women taking carbamazepine)

voriconazole

zopiclone.

Carbamazepine may reduce the anti-blood-clotting effect of coumarin anticoagulants such as warfarin, phenprocoumon or acenocoumarol. If you are taking carbamazepine in combination with one of these your blood clotting time (INR) should be regularly monitored, particularly when starting or stopping treatment and after any dose changes.

Carbamazepine may make the antiplatelet medicine clopidogrel less effective at reducing the risk of blood clots. This combination of medicines is not recommended.

If carbamazepine is taken with diuretics such as furosemide or bendroflumethiazide or antidepressants such as amitriptyline or fluoxetine there may be an increased risk of a fall in the level of sodium in the blood. Your doctor may want to monitor the level of sodium in your blood if you are taking carbamazepine with one of these medicines.

If carbamazepine is taken with lithium there may be an increase in brain and nervous system side effects, eg confusion, drowsiness, weakness, lethargy and tremor.

If carbamazepine is taken with isoniazid or sodium valproate there may be an increased risk of side effects on the liver.

Other medicines containing the same active ingredient

Carbamazepine tablets are also available without a brand name, ie as the generic medicine.

If you are taking carbamazepine for epilepsy you should, whenever possible, always take it in the same form, ie as Tegretol tablets, chewtabs, liquid, suppositories or prolonged release tablets, or as generic carbamazepine tablets made by the same manufacturer. This is because carbamazepine in different forms or made by different manufacturers may differ in the way it is absorbed into the body, which could either reduce the effect of the medicine and increase the risk of seizures, or increase the effect of the medicine and increase the risk of side effects. You should check with your pharmacist if you are ever dispensed your carbamazepine in a different form or made by a different manufacturer.

Further reading

For background information about our medicine factsheets, including the references used to produce them, click here.

The materials in this web site are in no way intended to replace the professional medical care, advice, diagnosis or treatment of a doctor. The web site does not have answers to all problems. Answers to specific problems may not apply to everyone. If you notice medical symptoms or feel ill, you should consult your doctor - for further information see our Terms and conditions.

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